Double pipe heat exchanger



1937. J. c. MAHONEY DOUBLE PIPE HEAT EXCHANGER 2 Sheets-Sheet 1 Filed June 16, 1936 grvuc/wlon Jafm 7. Mfume Nov. 16, 1937. J c MAHQNEYI 2,099,493

DOUBLE PIPE HEAT EXCHANGER Filed June 16, 1936 2 Sheets-sheaf 2 Q: I I I o 2; lm\|\\\\\ m l 4 l? 0 w 4 5 O I a W A o 3 wuwwtoc 1.727191] 53 Mia/501727 SUM 1 Patented Nov 16, 1937 PATENT OFFICE- DOUBLE PIPE HEAT EXCHANGER John C. Malroney, Westiield, N. J., assignor to Henry Vogt Machine Co. Inc., Louisville, Ky., a corporation of Kentucky Application June 16, 1930, Serial No. 85,614

2 Claims.

This invention relates to double pipe heat exchangers of the type in which the pipes are arranged in multiple tiers or rows and connected serially at their ends.

5- The general object of the invention is to provide a double pipe apparatus for the indirect exchange of heat between fluids, which can be completely and rapidly disassembled for purposes of cleaning or inspection, and in which the inner tubes are free floating. Hence the tubes may vary in length according to temperature without setting up untoward strains in the structure of a the heat exchanger. Heretofore in double pipe exchangers it has been the general practice to provide for expansion by using a packed joint or gland in which the inner tube can move as its length changes with temperature. Such exchanger designs can be disassembled for cleaning but the process of removing the inner tubes is labor-consuming and usually entails the expens'e of replacing damaged gland packing. Further such designs are not adapted tooperation under high pressures or high temperatures.

Where devices have been offered with provisions 2 to compensate for expansion and to withstand pressure and temperature these cannot be readily or completely disassembled.

This invention has particular application to oil refining processes where one or both of the mediums to be handled contain solids which tend to deposit out or where the mediums are likely to decompose to form solids. Typical of these mediums wouldbe the discharge from a cracking or reforming still, the heavy tar from a cracking operation, and the asphalt produced by vacuum distillation. Where any of these fluids is to be handled the exchanger must be easily disassembled to allow for cleaning. My invention provides for the easy disassembling ot the inner tube connections at one or both ends to I permit the ready withdrawal of the inner tubes.

intermediate return bends in an alternative form of the invention; and

Figure '7 is a sectional view showing a modified form of connection between an inner tube and the return bend.

Referring now in detail to the several figures. the numeral i represents in general a heat exchanger consisting of vertically-stacked rows of double pipes each consisting of an outer tube 2 and an inner tube 3, said tubes being preferably coaxial and of such relative size as to leave an 20 annular space within the outer tube. It will be understood that the double pipes may be optionally arrangedin horizontal rows ii convenience -oi? installation so requires without affecting the For purposes of 25 operation of the exchanger. illustration the vertical arangementis shown and subsequent references relate to the vertical arrangement. J

In the illustrated form of the invention the outer tubes 2 are secured in tube sheets 3' in any 30 suitable manner as by welding or by expanding and the tube sheets are shown as being divided into small individual sections each receivingfour tubes arranged in side-by-side pairs. The extent of the tube sheets and the number of tubes re- 35 ceived by them is, of course. a matter of choice or design and not affecting the patentability of the invention. At the inlet and outlet the tubes 2 are received in small tube sheets 4, each receiving two side-by-side tubes.

Figure 3 shows that the inner 'tubes 3 of successive rows project freely through the outer tubes, and being a little longer they extend into 'chambers 5 and 6 formed within headers I.

These headers might be integral castings or stampings, but in the interest 01' manufacturing economics they areshown as made up of three sections 8, 9, and l0. The headers are bolted to the adjacent tube sheets in fluid-tight man- 50 ner, a gasket ll intervening. Each proiecting tube end is expanded or threaded in permanent and fluid-tight manner into end fittings l3. Where the tubes are expandedvinto the end flttings the fittings are preferably grooved so that in the expanding operation, the tube metal will .fiow into the grooves forming the shoulder l2 and improving the tightness of the metal-to-metal joint. The end fittings consist of a sleeve portion l6 engaged with the ends of the inner tubes, having parallel ears i1 and I! at diametrically opposite points, leaving a space in between. The outer ends of the sleeve portions ii are internally flared as at I3 forming a seat for the correspondingly tapered ends of the U-bend 20. The U-bend bridges the space between vertically adjacent inner tubes and lies between the ears I! and I3 of vertically adjacent fittings i3.

The ears [1 and i8 are formed with slots 2| through which extend the ends of the locking element or dog 22, see Figures 3 and 5.v The dog has a threaded aperture 23 receiving a screw bolt 24, the lower end of which bears against the shoulder 25 formed on the U-bend. The entire fittings i3 including the ears l1 and i8 are sufilciently narrow to freely pass through the outer tubes 2 in the act of withdrawing the inner .tubes to which the said fittings are permanently attached.

In the act of assembling, the U-bends are pushed into place, the dogs 22 put in position one at a time, of course, with their endsprojecting through the slots 2|, and the bolts 24 are then inserted and turned down until they abut the shoulders 25 on the U-bends. At this time the adjustment will be loose but by continuing to screw down the bolts 24 the cross bars 22 will back out until their ends engage the outer ends of the slots 2|, whereupon the bolts will press rigidly against the U-bend forcing the tapered ends 0 the same into fluid-tight engagement with the tapered ends of the fittings i3.

For taking out the inner tubes the process will be reversed. After the U-bends have been removed the tubes may be individually withdrawn.

With regard to the first and last double pipes in the series, the respective inlet and outlet ends of the outer tubes of which are permanently connected to the tube sheets, it is merely necessary to remove the U-bend at one end of the inner tube and then to disconnect bolts 23 and header 21. wh reupon the inner tube may be withdrawn in a outward direction. It will be observed from the several figures that one end of the inlet and outlet tubes, and both ends of the intermediate tubes are free-floating so that the inner tubes may expand freely under differences in temperature without setting up any strain in the structure of the heat exchanger.

For reasons of economy of size and material in the tube sheet and header construction, the axes of vertically adjoining tube assemblies 2, 3, and 5 are in divergent rather than parallel relationship with one another. The axes of horizontally adjoining tube assemblies remain however' in parallel relationship. The flared seats. of the end fittings in cooperation with the tapered ends of the return bendsadjust themselves to accommodate the pitch ordivergence of the interconnected tubes without impairing the tightness of the joints. The ioint between the end fittings and the U-bend may also be spherical in contour rather than conical as indicated in Figure 7, in

which 39 is the spherical seat in the coupling and 40 the spherical end on the U-bend.

Figure 2 shows that the fluids which are to be placed in heat exchanging relation enter respectively by the inlets 28 leading to the innertubes, and 29 communicating with the outer tubes, and that the fluids leave the heat exchanger by way of the respective outlets 29% and 30, Insofar as the structure of the apparatus is concerned and fiow of the fiuid streams emerging from and entering the outer pipes. The bame is preferably vented as at 32' to permit access of liquid to the otherwise blind space 33 and to equalize pressure both inside and outside of the battle. The purpose of the baiiie is to prevent substantially lateral impact of the two parallel flow streams as they enter the header I, and to direct them in an approximation to streamlined flow. The baflie in cooperation with the U-bend forms passages which approach uniformity in cross section. The turbulent flow condition which would otherwise be set up in this zone by the interfering action of the two parallel streams is avoided to a large extent by the interposition of this dividing baffie. Elimination of frictional loss which is refiectedin power costs has a definite economic value.

In further expansion of this baflles function, it

has been found. in .actual practice that unless some means is used to direct two parallel streams in an individual header, that the pressure losses due to impact of the opposing streams are high.

The modified form of the invention illustrated in Figure 6 proposes to connect the ends of ver tically adjacent inner tubes to tube sheets at one end substituting said tube sheets for the removable U-bend illustrated in connection with the first described form but leaving the other ends of theinner tubes detachably connected to the removable U-bends 20.

Figure 6 shows that the outer tubes 2 are connected to a tube sheet 3' similar in all respects to that illustrated in connection with Figure 1 and the inner tubes 3 which project a slight distance outwardly of the outer tubes, are connected to a tube sheet 34 which preferably lies against the tube sheet 3' in gasketed relation and occludes scribed in connection with the first form of the invention. The U-bend 35 may then be grasped and the vertically adjacent pair of inner tubes 3 pulled out at the same time. If it is desired to withdrawthem individually, the lJ-bend- 35 is taken off and either portion of the tube sheet 34 drawn out together with the attached inner tube. The substitution of the tube sheet 34 for the construction shown in connection with Figure 3 does not materially defeat the capacity of the inner tubes to expand for they are free-flowing at the opposite end.

While I have in the above description disclosed what I believe to be a preferred and practical turn bends for preventing lateral circulation of embodiment of the invention, it will be understood to those skilled in the art that the details of construction as shown and described are by way of example and not to be construed as limiting the scope of the invention as claimed.

What I claim is:

1. A heat exchanger comprising a plurality of double pipe elements arranged in rows, each including an inner tube and a surrounding outer tube, said tubes being arranged to define an annular space between them, the ends of outer tubes at one end of said exchanger being supported by a tube sheet and opening in the outer face of said tube sheet, a header secured against said tube sheet defining therewith a chamber with which two or more adjacent pair of outer tubes com members, said coupling members including clamping means for securing said return bends in place, a bafiie within said header between adjacent rethe liquid within said header and means for independently serially connecting the inner tubes of said rows and the outer tubes of said rows at the opposite end of said exchanger.

2. A heat exchanger comprising a plurality of double pipe elements arranged in rows, each including'an inner tube and asurrounding outer tube, said tubes being arranged to define an annular space between them, said double pipe elements being serially connected both as to the inner and outer tubes, the outer tubes at both ends bein supported by tube sheets and opening into the outer faces of said tube sheets, and connectingdevices at one end of a pair of adjacent inner tubes comprising a removable return bend permitting said inner tubes to be withdrawn from said outer tubes and means for securing said return bend to said inner tubes, a tube sheet receiving the opposite ends of said inner tubes, said last named tube sheet lying against the adjacent tube sheet which supports the outer tubes and occluding said outer tubes, a return bend secured to the tube sheet receiving said inner tubes and a lateral connection between said outer tubes.

JOHN C. MAHONEY. 

